Recurrence risk of congenital anomalies--the impact of paternal, social, and environmental factors: a population-based study in Denmark.

The authors investigated the recurrence risk of congenital anomalies as a function of changes in genetic and environmental factors in single births following the birth of a child with an anomaly. The study is a population-based historical follow-up using the Danish Medical Birth registry, hospital discharge diagnoses, and Statistic Denmark's Fertility Database. The investigators identified 8,671 women who gave birth to a child with a diagnosed malformation between 1980 and 1992 and had a subsequent birth. Following the birth of an affected infant, 474 (5.5%) women gave birth to another child with a malformation, 155 of which (1.8%) were similar to the malformation of the older sib or half sib. When the father changed between the two births, the risk of a similar anomaly was significantly reduced (odds ratio (OR) = 0.26, 95% confidence interval (CI) 0.11, 0.65). Higher social status at enrollment was associated with a lower recurrence risk (OR = 0.67, 95% CI 0.45, 0.99, for the middle status group and OR = 0.49, 95% CI 0.30, 0.81, for the highest status group), independently of partner change. A rise in social status between the two births was marginally associated with a decline in the recurrence risk. No variation in the recurrence risk associated with change of municipality or occupation was seen.